I went crib mattress shopping the other day, and I noticed that while all of the mattresses are firm, some are firmer than others. There was one mattress that was so firm it almost felt like a rock -- is that how firm a crib mattress is supposed to be? Also, I liked an organic cotton mattress there but it didn't seem as firm. I know mattresses for babies are supposed to be firm but I don't think I'm good at judging just how firm a mattress should be. Any advice? Thanks!